dual monitor problem

Discussion in 'Mac Pro' started by pjsmith67, Jan 7, 2013.

  1. pjsmith67 macrumors newbie

    May 21, 2010
    I'm having a problem with dual monitors on my Mac Pro. When the machine wakes up, it does not recognize the second monitor. I have to unplug the display cable and plug it back in, which is a real pain.

    My setup:

    Mac Pro Mid 2010, single quad core Xeon processor
    ATI Radeon HD 5770 1024mb graphics card with 2 mini display ports, one DVI
    Lenovo 21.5" monitor plugged into the DVI
    ViewSonic 2230W plugged into a mini display port
    Mountain Lion 10.8.2

    The ViewSonic is the one that it does not recognize. However, I have swapped out other monitors with the same result so i don't think its the monitors.

    Anyone know anything about this? I have not been able to find a direct answer to this but my research shows that it may be a ML bug.


  2. nigelbb macrumors 65816

    Dec 22, 2012
    I seem to recall getting this on my wife's Mac Pro when she had a 5770 & the way round it is to use both mini display ports of course you will need a MDP to DVI adaptor but don't get the Apple one as that isn't guaranteed to work with any display other than an ACD.
  3. bax2003 macrumors 6502a


    Dec 25, 2011
    This is definitely not normal. I have both 5870 and 5770 in MP 5.1 and use at a moment both of them for two displays. You will start having problems when you add 3rd monitor, either DVI or Converted (eg. Mini DP to HDMI).

    You should not have problems with ANY two monitors. So either very low quality cable, HW problem (5770) or OS X problem.
  4. pjsmith67 thread starter macrumors newbie

    May 21, 2010
    Hmmm... I wonder if its because the 2nd monitor is connected using display port to VGA adapter? I used the same cable with the other monitors I tested as I did not have another cable to use.

    May have to run out to the local Apple store and get a display port to DVI cable. The other monitor has both VGA and DVI-D ports.
  5. nigelbb macrumors 65816

    Dec 22, 2012
    We never had a problem with three monitors on the 5770 using two powered MDP->DVI converters & a dual link DVI cable.
  6. pjsmith67 thread starter macrumors newbie

    May 21, 2010
    dual monitor problem - solved

    It appears that waking a monitor from sleep with a display port to VGA cable does not work, at least on my system. I swapped out that monitor with another one that has DVI input and it worked using a display port to DVI cable.


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